The present invention relates generally to lighting systems and, more particularly, to flexible, compact, battery operated LED arrays that are able to be conformably mounted over surfaces with compound curvatures.
Light emitting diode (LED) lighting systems are commonly used as individual elements or in groups for illuminating a large variety of objects. Typically, such lighting systems are arranged in generally linear rows and are disposed so as to provide decorative, advertising or safety oriented light sources. Conventionally, these lighting system rows might be attached to a wire string such as exemplified by a xe2x80x9cstring of lightsxe2x80x9d used for Christmas tree decorations. Lighting systems constructed of LED light strips, are particularly advantageous when compared to bulb or lamp based lighting systems in that light strips are relatively inexpensive to manufacture and consume a relatively small amount of power. However, conventional lighting systems, whether bulb based or LED based are limited in usefulness due to the difficulty of attaching them to various structures and that these types of lighting systems are often inflexible in their design and require permanent mounting to attached structures.
Present LED light strips typically composed of circuitry including a number of LEDs mounted onto substrates by having their whisker leads soldered onto connection points provided for such purpose and connected to electrical conductors. The entire circuitry is typically encased within a protective sheathing and coupled to a power source for selective LED illumination. Such LED lighting systems are utilized in a variety of indoor and outdoor configurations, but suffer from significant drawbacks in that the LED lamps are rather large, are exposed to the elements and are very susceptible to damage by wind, water, etc. Additionally, these LED lighting systems require that the LED lamps be adhered to a mounting substrate by having their whisker leads soldered thereto. Once the LED lamp is affixed to the substrate, excess lead material must be removed and the resulting assembly mounted on a support that is substantially flat in order that the viewing angle for the component LED lamps is not exceeded.
Conventional LED based lighting systems typically utilize dual-lead cannister or dome shaped LED lamps as a light source. These dome or cannister shaped LED lamps are typically about 5 to 7 millimeters tall and from about 3 to about 5 millimeters in diameter, exclusive of their electrically conductive leads. Although available in various colors, a typical conventional LED lamp will have a light intensity (expressed in millicandles or mcd) of from about 8 to about 50, when implemented in Galium Phosphide (GaP) with a viewing angle of approximately 10 to 15 degrees. Needless to say, when such lighting systems are mounted over radiused or other conformal surfaces, it requires very little displacement to move the beam angle of a particular LED lamp outside the viewing arc.
For example, LED lighting systems have been used in the prior art as auxiliary brake lights in automotive applications. Five millimeter LEDs are typically used to supplement original equipment vehicle brake lights and incorporated onto a mounting surface which is adhered or secured to the rear portion of a vehicle. Considerable differences in angles of inclination and curvatures of rear window glasses and other vehicular surfaces limit the usefulness of such LED lighting systems. For example, when an auxiliary brake light is mounted on a vehicle provided with a rear window glass having a strong curvature, an optimum mounting or viewing angle for each LED lamp may not be achieved. For this reason, a single type of auxiliary light, capable of being placed on various portions of all manners of vehicles, is very difficult to economically manufacture.
In addition, many conventional 5 millimeter LED lighting systems have their LED lamps spaced-apart from one another to such an extent that the individual component light sources are easily discernable. In other words, instead of a viewer perceiving a lighting system having uniform brightness, the viewer perceives intermittent bright spots, corresponding to LED light source positions, over the surface area of the lighting system. Various prior art systems have attempted to address this problem by placing distortion lenses (or diffusion lenses) over the LED light sources, but these distortion lenses are not altogether effective and further tend to reduce the overall brightness of the lighting system. Conventional 5 millimeter LEDs, even if disposed as close together as possible, still exhibit inconsistent light distribution due to their relatively shallow viewing angles. Prior art lighting systems are thus relatively large, visually unpleasing and relatively expensive and time consuming to manufacture. Thus, in addition to exhibiting relatively poor performance, their size and shape tend to make them objectionably obtrusive.
Accordingly, what is needed is a flexible, low-profile, bright, easily manufactured and visually pleasing light emitting diode system which can be mounted easily, in any desired form over radically radiused compound curvatures, for a variety of uses. Further, such a light emitting diode system needs to provide a constant source of light while operated by a relatively low voltage battery source.
A flexible, low profile, high density array of light emitting diodes includes a plurality of surface mount light emitting diodes affixed to the surface of a flexible printed circuit board substrate, the substrate adapted to support and electrically interconnect surface mount electronic components. Each of the plurality of surface mount light emitting diodes has a particular dimension, less than or equal to about 3 mm, and is disposed on the flexible printed circuit board substrate at varying distances in order to define light intensity outputs of from about 2 to about 20 candles per square centimeter.
The flexible printed circuit board substrate might be configured as a flex circuit, or might be configured as a rigid flex circuit board, each pre-manufactured to define mounting locations for each of the plurality of surface mount light emitting diodes. The flexible printed circuit board substrate, in combination with the surface mount light emitting diodes, defines a conformable, bendable lighting array configured for mounting upon surfaces with compound curvature.
The surface mount light emitting diodes are configured, upon the flexible substrate, in an array comprising regular sets of series-connected diodes, the series-connected sets coupled in parallel fashion to one another. The number of light emitting diodes comprising a series-connected set defines a forward voltage drop for the set. The forward voltage drop, in turn, defines a supply voltage value sufficient to activate the diodes of each series-connected set. Surface mount diodes comprising the array might have forward voltage drops anywhere in the range of from about 1.7 to about 5.0 volts.
In a further aspect of the invention, the flexible, low profile, high density lighting system further includes a housing configured to hold and support a flexible lighting array and so encloses the array as to protect it from impact and the elements. The housing might be transparent and might further be colored. Alternatively, the housing might be water clear and the plurality of surface mount light emitting diodes might be colored.